Evidence suggests that a variety of neuroanatomical abnormalities are present in portions of the brain connected with the limbic system. Recent studies have implicated neuroanatomical changes in the frontal cortex, hippocampus, nucleus accumbens and mediodorsal thalamic nucleus of schizophrenics. Past neuroanatomical studies have generally focused on the hippocampus and frontal cortex, with little consideration of the involvement of subcortical regions such as the thalamus that are critical links in limbic system circuitry. The current proposal will build upon recently obtained information implicating neurochemical, neuroanatomical and neurofunctional disturbances in the thalamus of schizophrenics. The study will provide the first neuroanatomical survey of all thalamic nuclei in schizophrenia. Similar surveys of thalamic nuclei in Alzheimer's disease have revealed unexpected and profound cell loss in specific thalamic nuclei, while many nuclei were not severely affected. Information about the relative involvement of specific thalamic regions may provide clues to neurofunctional and behavioral abnormalities in schizophrenia. Stereological techniques will be used to estimate neuronal populations in previously collected post-mortem tissue from the Waco VAMC Brain Collection. The results will indicate whether changes in cell counts occur specifically in limbically-associated medial and anterior thalamic nuclei, as hypothesized, or whether cell loss is distributed more evenly throughout the thalamus. The findings will begin the characterization of neuropathological changes in this important center of limbic system neurotransmission.